U.S. patent number 7,950,902 [Application Number 11/492,110] was granted by the patent office on 2011-05-31 for cooling channel formed in a wall.
This patent grant is currently assigned to SNECMA. Invention is credited to Emmanuel Pierre Camhi, Laurent Crouilbois, Jean Pierre Mareix, Didier Pasquiet.
United States Patent |
7,950,902 |
Camhi , et al. |
May 31, 2011 |
Cooling channel formed in a wall
Abstract
A wall in which there is formed at least one cooling channel,
said wall being cooled by cool air flowing in the channel, the
channel comprising a hole and a diffusion portion, the hole opening
out at one end into the inside surface of the wall, and at its
other end into the diffusion portion where it forms an orifice, the
diffusion portion flaring around said orifice and opening out into
the outside surface of the wall, the diffusion portion having a
bottom whose front end is substantially plane, sloping, and
extending in front of the orifice, and also having a margin
extending behind, round the sides, and in front of the orifice,
said margin joining the sides of the front end. A method and an
electrode for making such a cooling channel. A turbomachine blade
presenting such a wall.
Inventors: |
Camhi; Emmanuel Pierre (Fuveau,
FR), Crouilbois; Laurent (Brunoy, FR),
Mareix; Jean Pierre (Chartrettes, FR), Pasquiet;
Didier (Boissise le Roi, FR) |
Assignee: |
SNECMA (Paris,
FR)
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Family
ID: |
37682465 |
Appl.
No.: |
11/492,110 |
Filed: |
July 25, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070025852 A1 |
Feb 1, 2007 |
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Foreign Application Priority Data
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Jul 26, 2005 [FR] |
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05 07924 |
Jan 12, 2006 [FR] |
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06 50103 |
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Current U.S.
Class: |
416/97R |
Current CPC
Class: |
B23H
1/04 (20130101); B23H 9/10 (20130101); B23K
35/0216 (20130101); F05D 2250/232 (20130101); Y10T
29/49341 (20150115); F05D 2230/12 (20130101); Y10T
29/49336 (20150115); F05D 2230/13 (20130101); F01D
5/186 (20130101) |
Current International
Class: |
F01D
5/18 (20060101) |
Field of
Search: |
;416/95,96R,97R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 267 718 |
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May 1988 |
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EP |
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1 228 832 |
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Aug 2002 |
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EP |
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1 517 003 |
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Mar 2005 |
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EP |
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2000-064806 |
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Feb 2000 |
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JP |
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2000-141069 |
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May 2000 |
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JP |
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2000-141069 |
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May 2000 |
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JP |
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2005-090511 |
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Apr 2005 |
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JP |
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Other References
"Zuckerhut (Lebensmittel)" aus Wikipedia, der freien Enzyklopadie
(2 Seiten), Aug. 18, 2009. cited by other .
Official Action in corresponding Japanese Patent Application No.
2006-200296 dated Jan. 11, 2011. cited by other.
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Primary Examiner: Yu; Justine R.
Assistant Examiner: Younger; Sean J
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier
& Neustadt, L.L.P.
Claims
What is claimed is:
1. A wall element in which at least one cooling channel is formed,
said wall element comprising: an inside surface and an outside
surface cooled by cool air flowing along said channel, wherein the
channel includes a hole and a diffusion portion, the hole opening
out at one end thereof in the inside surface, and at an other end
in the diffusion portion where the hole forms an orifice, the
diffusion portion flaring around said orifice and opening out in
the outside surface, wherein a front end of a bottom of the
diffusion portion is substantially planar, slopes in a thickness of
the wall, extends forwards from the orifice in a cool air flow
direction, wherein the diffusion portion includes a margin
extending behind the orifice, along sides of the diffusion portion,
and in front of the orifice, said margin joining the sides of the
front end of the bottom of the diffusion portion, and wherein the
margin and the front end of the bottom of the diffusion portion are
inscribed in a cone having a rounded end and a conical surface that
includes a flat portion.
2. A wall element according to claim 1, wherein an outline of the
front end of the bottom of the diffusion portion is in the form of
a triangle with one vertex of the triangle pointing towards said
orifice so as to widen the cool air flow leaving the hole.
3. A wall element according to claim 1, wherein an angle formed
between the margin and the front end of the bottom of the diffusion
portion in a plane perpendicular to the front end is greater than
90.degree..
4. A wall element according to claim 1, wherein an axis of said
cone is parallel to the axis of the hole.
5. A hollow turbomachine blade including a wall element in which at
least one cooling channel is formed, said wall element comprising:
an inside surface and an outside surface suitable for being cooled
by cool air flowing along said channel, wherein the channel
includes a hole and a diffusion portion, the hole opening out at
one end thereof in the inside surface, and at an other end in the
diffusion portion where the hole forms an orifice, the diffusion
portion flaring around said orifice and opening out in the outside
surface, wherein a front end of a bottom of the diffusion portion
is substantially planar, slopes in a thickness of the wall, extends
forwards from the orifice in a cool air flow direction, wherein the
diffusion portion includes a margin extending behind the orifice,
along sides of the diffusion portion, and in front of the orifice,
said margin joining the sides of the front end of the bottom of the
diffusion portion, and wherein the margin and the front end of the
bottom of the diffusion portion are inscribed in a cone having a
rounded end and a conical surface that includes a flat portion.
6. A turbomachine including a hollow blade having a wall element in
which at least one cooling channel is formed, said wall element
comprising: an inside surface and an outside surface suitable for
being cooled by cool air flowing along said channel, wherein the
channel includes a hole and a diffusion portion, the hole opening
out at one end thereof in the inside surface, and at an other end
in the diffusion portion where the hole forms an orifice, the
diffusion portion flaring around said orifice and opening out in
the outside surface, wherein a front end of a bottom of the
diffusion portion is substantially planar, slopes in a thickness of
the wall, extends forwards from the orifice in a cool air flow
direction, wherein the diffusion portion includes a margin
extending behind the orifice, along sides of the diffusion portion,
and in front of the orifice, said margin joining the sides of the
front end of the bottom of the diffusion portion, and wherein the
margin and the front end of the bottom of the diffusion portion are
inscribed in a cone having a rounded end and a conical surface that
includes a flat portion.
7. A wall element according to claim 4, wherein the axis of the
hole is offset towards the outside surface of the wall.
8. A wall element according to claim 1, wherein an angle between an
axis of the hole and the outside surface is less than
90.degree..
9. A wall element according to claim 8, wherein the angle is
between 15.degree. and 80.degree..
10. A wall element according to claim 1, wherein the flat portion
is formed at angle between 2.degree. and 45.degree. relative to the
outside surface.
11. A wall element according to claim 1, wherein an angle between
an axis of the hole and the outside surface is greater than an
angle between the outside surface and the flat portion.
Description
The invention relates to a method of forming a cooling channel in a
wall, to an electrode used for implementing the method, to a wall
element in which a cooling channel is formed, and to a hollow
turbomachine blade including a wall element of this type.
FIELD OF THE INVENTION
More precisely, the invention relates to a wall element of the type
comprising an inside surface and an outside surface, the outside
surface being suitable for being cooled by cool air flowing in said
cooling channel. In addition, the cooling channel is of the type
comprising a hole and a diffusion portion, the hole opening out at
one end into the inside surface of the wall and at its other end
substantially into the bottom of the diffusion portion by forming
an orifice, and the diffusion portion flaring away from said
orifice and opening out into the outside surface of the wall.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 6,183,199 B1 shows an example of a wall element for a
hollow blade of a turbojet turbine, the element being pierced by a
cooling channel of the above-specified type. In that example, the
hole of the channel and its diffusion portion are made by
electro-erosion in a single step, using a single electrode whose
tip presents a front portion of a shape that corresponds to that of
the hole and a rear portion of a shape corresponding to that of the
diffusion portion of the channel.
An electrode of that type is described and shown in U.S. Pat. No.
4,197,443 to which reference is made in U.S. Pat. No. 6,183,199 B1.
As can be seen, the shape of that electrode is particularly
complex. In addition, in general manner, forming a channel by
electroerosion using known methods remains an operation that is
lengthy and expensive.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the invention is thus to provide an alternative to
known methods, making it possible to form a cooling channel of the
above-specified type, more quickly and at lower cost.
To achieve this object, the invention provides a method wherein
said wall is pierced to make said hole, and wherein an indentation
is formed in said wall in order to form said diffusion portion, in
two distinct steps.
In the method of the invention, it is thus possible to use
techniques and materials that are different for making the hole and
for making the diffusion portion.
To make the hole, it is possible to pierce the wall by
electroerosion or by using a laser.
Advantageously, laser piercing techniques are used, since these
techniques are much faster and much less expensive than
electroerosion techniques. Thus, to pierce a wall of a hollow
turbine blade by laser, generally only a few tenths of a second are
required.
Nevertheless, if it is desired to perform the piercing and the
diffusion portion by electroerosion, then two different electrodes
are used for each of said portions. The electrodes are simpler in
shape than the electrodes that have been used in the past, so they
are easier and less expensive to make. For example, for the
piercing, it is possible to use an electrode that is
cylindrical.
According to another aspect of the invention, in order to make the
diffusion portion, an electrode is used in which the tip of the
electrode is in the form of a cone with a rounded end and with a
conical side surface that presents a flat, the axis of the cone not
intersecting the flat.
The above-specified shape for the electrode makes it possible
firstly to avoid creating a sharp angle in the bottom of the
diffusion portion, where sharp angles generally constitute starter
zones for cracks.
Secondly, an electrode of that shape and of appropriate dimensions
relative to the hole makes it possible to form a diffusion portion
of a shape that is sufficiently broad and flared to ensure that,
given the tolerances involved in making the hole and the diffusion
portion, and regardless of the position of the hole relative to the
diffusion portion, the diffusion portion provides good diffusion
(i.e. good guidance and good spreading) of the stream of air
leaving the hole.
The invention also provides a wall element having a new type of
cooling channel formed therein. Such a channel may be obtained
using the method and the electrode of the invention.
The channel includes a diffusion portion with a bottom whose front
end is substantially flat, sloping in the thickness of the wall and
extending in front of the orifice in the flow direction of the cool
air, and a rearwardly-extending margin on the sides and at the
front of the orifice, said margin joining the sides of the front
end of the bottom.
Advantageously, the angle formed between the margin and the front
end of the bottom in a plane perpendicular to the bottom is not
"sharp" in the sense that it is strictly greater than 90.degree..
This avoids creating crack-starter zones.
Finally, the invention provides a hollow gas-turbine blade
including a wall element of the above-specified type.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention and its advantages can be better understood on
reading the following detailed description. The description refers
to the accompanying figures, in which:
FIG. 1 is a section showing an example of a wall element of the
invention including a cooling channel;
FIG. 2 is a perspective view of the tip of the electrode used for
making the diffusion portion of the FIG. 1 channel;
FIG. 3 is a plan view of the FIG. 1 channel seen looking along the
direction III that is orthogonal to the outside surface of the
wall;
FIG. 4 is a view of the FIG. 1 channel seen looking along the
direction IV, i.e. along the piercing axis of the channel; and
FIG. 5 is a section view on plane V-V of FIG. 3.
MORE DETAILED DESCRIPTION
With reference to FIGS. 1, 3, 4, and 5, there follows a description
of an example of a wall element of the invention.
Said wall element presents an inside surface 3 and an outside
surface 5. This element belongs to a wall 1 of a hollow gas-turbine
blade, such as a high pressure turbine blade of a turbojet. This
type of hollow blade has an internal cooling passage 4 defined in
part by the inside surface 3, said passage being fed with cool
air.
The outside surface 5 of the wall is subjected to the hot gas
passing through the turbine and it therefore needs to be cooled.
For this purpose, cooling channels are provided in the wall 1. At
least some of these channels are of the same type as the channel
shown in FIG. 1. This channel 6 passes cool air coming from the
internal cooling passage 4 of the blade and delivers this cool air
to the outside surface 5 in order to cool it. The channel 6
comprises two portions: an adjustment portion formed by a hole 7,
and a diffusion portion 9 formed by an indentation formed in the
wall 1 in its outside surface 5.
The hole is said to be an adjustment portion since the minimum
section of the hole 7 serves to adjust the rate at which air flows
along the channel 6. Advantageously, the hole 7 is simple in shape.
In the example shown, the hole 7 is inscribed in a circular
cylinder. In addition, the axis B of the hole 7 is inclined at an
angle G relative to the outside surface 5 (or if this surface 5 is
not plane, relative to the tangent thereto on the axis B). The
angle G is less than 90.degree., and preferably lies in the range
15.degree. to 80.degree., so as to direct the stream of air F
towards the outside surface 5 so that it remains as close as
possible thereto. In other words, it is desired to make the
velocity vectors of the air stream F at the outlet from the channel
6 as nearly parallel as possible to the plane of the outside
surface 5.
In order to direct the stream of air F better against the outside
surface 5 and in order to spread this stream of air F in the plane
of the outside surface 5, the channel 6 presents a diffusion
portion 9 following the hole 7. This diffusion portion 9 flares
around the orifice 11 through which the cool air leaves the hole 7.
This orifice 11 is situated preferably substantially in the bottom
of the diffusion portion 9 relative to the outside surface 5. In
front of the orifice, in the flow direction of the stream F, the
diffusion portion 9 has a bottom whose front end 13 is
substantially plane, sloping in the thickness of the wall at an
angle g relative to the outside surface 5. The angle g preferably
lies in the range 2.degree. to 45.degree., and in any event it is
smaller than the angle G so that the stream of air F, as guided by
the front end 13 of the bottom is directed towards the outside
surface 5.
The front end 13 of the bottom encourages the stream of cool air F
leaving the hole 7 to come close to the outside surface 5. This air
stream thus remains in contact with the outside surface 5, thus
making it possible firstly to cool the surface 5 by heat exchange
and secondly to create a protective film of air on said surface 5
that keeps the hot gas of the medium in which the wall 1 is
situated at a distance from said surface 5.
Advantageously, the outline of the front end 13 of the bottom is
generally triangular in shape, having one of its vertices pointing
towards said orifice 11 (see FIGS. 3 and 4), thus enabling the air
stream F leaving the hole 7 to be spread, and thus cooling and
protecting a larger portion of the outside surface 5. Naturally,
the base remote from said vertex is wider than the orifice 11, so
as to widen the air stream F.
At the rear end, on the sides and in front of the orifice 11, there
is a margin 15. The margin 15 goes around the orifice 11 in part
and towards the front it joins the sides of the front end 13 of the
bottom.
In the example shown in FIG. 5, the junction zones between the
margin 15 and the front end 13 present edges 17. The angle P formed
in these edges between the margin 15 and the front end 13 itself,
in a plane perpendicular to the front end 13, is strictly greater
than 90.degree. so as to avoid weakening the wall element 1. The
angle P is measured between the tangent T to the margin 15 at the
edge 17, and the front end 13 of the bottom, as shown in FIG.
5.
It is also possible to provide rounding in each junction zone in
order to avoid creating any edges. Under such circumstances, the
angle P is measured between the general direction of the margin 15
and the front end 13 of the bottom.
In the example of FIG. 1, the rear portion of the margin 15 flares
rearwards from the orifice 11 and then presents a
forwardly-directed lip 12 in the outside surface 5. This lip 12
helps guide the stream of cool air forwards.
The front end 13 of the bottom and the margin 15 are inscribed in a
cone 23 having a rounded end 24 and a conical surface 25 that
presents a flat 26. The front end 13 of the bottom corresponds to
the flat 26, and as can be seen in FIGS. 1 and 4, the margin 15
corresponds essentially in its rear portion with the rounded end 24
of the cone 23, and in its side and front portions with the conical
surface portions 25 adjacent to the flat 26. Advantageously, the
axis E of the cone 23 and the axis B of the hole 7 are parallel,
with the axis B preferably being offset towards the outside surface
5, as shown in FIG. 1.
With the shape of the cooling channel 6 in the wall element 1
described fully above, there follows a description of an
implementation of the method of, the invention enabling a channel
of this type to be formed.
In a first step of the method, the wall 1 is pierced by means of a
laser. Laser piercing techniques are known to the person skilled in
the art and they present the advantage of being fast and less
expensive than electro-erosion techniques.
Then, in a second step, the recess corresponding to the diffusion
portion 9 is formed in the wall 1 in its outside surface 5 by
electroerosion. Naturally, this second step could be undertaken
before the first.
For this second step, an electrode 20 is used that is of the type
shown in FIG. 2. The body of the electrode 21 is cylindrical while
the tip 22 of the electrode is in the form of a cone 23 having a
rounded end 24 and including a flat 26 in its lateral conical
surface 25. The flat 26 extends on one side of the cone 23 from a
point in the vicinity of the end 24 to the portion of the cone 23
where it is at its greatest flare, and beyond. The axis E of the
cone 23 does not intersect the flat 26: the flat therefore does not
intersect the end vertex 24 of the cone 23. The cone 23 is
symmetrical about a plane of symmetry S perpendicular to the flat
26 and containing the axis E of the cone 23. The half-angles Y of
the flare defined between the side edges 27 of the flat and the
plane S lie in the range 10.degree. to 30.degree., and are
preferably close to 15.degree..
As shown in FIG. 1, the indentation corresponding to the diffusion
portion 9 is formed by electroerosion, by pushing the tip 22 of the
electrode 20 into the wall 1 via its outside surface 5, the flat 26
being positioned to face said outside surface 5. Advantageously,
during this operation, the axis E of the cone 23 is oriented so as
to be parallel to the axis B of the hole 7, with these axes
preferably being offset so that the axis B is the closer to the
wall 1.
It should be observed that the presence and the size of the lip 12
of the margin 15 (i.e. the extent to which it extends rearwards)
depends on the radius of the curvature of the end 24 and on the
depth to which the electrode 20 is pushed in.
In general, when forming the indentation, the following are
selected: the shape of the electrode 21 and more particularly the
shape of the cone 23, the radius of the curvature of the rounded
end 24 and the position of the flat 26 (half-angles Y of the
flare); the position of the electrode, and more particularly the
orientation of the axis E of the cone 23 relative to the axis B of
the hole 7; and the penetration depth of the electrode 20 into the
wall 1; so as to form the front end 13 of the bottom in front of
the orifice 11 and a flared margin 15 behind and on the side of the
orifice 11 that meet the sides of the front end 13 where they form
two edges 17. These edges are sufficiently rounded to avoid
creating zones of weakness (see FIG. 5).
The presence of the rear margin 15 enables the diffusion portion 9
to be made with a certain amount of tolerance relative to the hole
7. This is shown in FIG. 4 where dashed lines show various
positions that the orifice 11 could occupy relative to the
diffusion portion 9. As can be seen, in all the examples shown, the
orifice 11 opens out completely into the diffusion portion 9 at a
position such that the cool air stream is guided by the diffusion
portion 9, thereby guaranteeing proper cooling of the outside
surface 5. Naturally, better diffusion is obtained when the orifice
11 opens out substantially into the bottom of the diffusion portion
9, as shown in continuous lines.
* * * * *